Exhaust gas emitted from an internal combustion engine is a heterogeneous mixture that contains gaseous emissions such as, but not limited to, carbon monoxide (“CO”), unburned hydrocarbons (“HC”) and oxides of nitrogen (“NOx”), as well as condensed phase materials (liquids and solids) that constitute particulate matter (“PM”). Catalyst compositions, typically disposed on catalyst supports or substrates, are provided in an engine exhaust system as part of an aftertreatment system to convert certain, or all of these exhaust constituents into non-regulated exhaust gas components.
One type of exhaust treatment technology for reducing emissions is a particulate filter (“PF”). The PF is designed to remove diesel particulate matter, or soot, from exhaust gas of an engine. The particulate matter removed from the exhaust is entrapped by, and entrained in, the PF. When accumulated soot reaches a predetermined level the PF is either replaced or regenerated. Replacement or regeneration facilitates that soot removal continues at desired parameters. In addition, many engines include an oxidation catalyst (“OC”) that oxidizes hydrocarbons and carbon monoxide into carbon dioxide and water. In some cases, the PF and OC are arranged in a single component.
Many engines include a controller having a soot out monitor that predicts soot accumulation in the PF. The soot out monitor employs complex algorithms that receive various engine operating parameters to predict soot accumulation levels in the PF. The operating parameters include duration and number of accelerations, duration of operation at constant RPM above idle, and idle time. Inaccurate soot accumulation predictions could lead to premature replacement or cleaning of a OC/PF. In addition, the various parameters used by the more complex algorithms require the use of application specific sensors that add to production costs and may require periodic maintenance and/or replacement. Accordingly, it is desirable to provide a less complex monitoring system that provides a more accurate depiction of PF health utilizing existing sensors.